But it’s not the best way to reach people who don’t want to hear from you. Bad lists won’t just stall your marketing efforts, they’ll actually undermine your business. If you don’t regularly clean your email lists to ensure everyone you email has a valid email address and actually wants to receive your stuff, here’s what you can expect to happen:

Since you probably don’t want any of those things to happen, we’re here to give you info on turning your bad email lists around. In this post, I’ll go over what bad and good email lists looks like, and what steps you can take to transform your bad ones into good ones. By the end, you’ll be in much better email marketing shape.

What a Bad Email List Looks Like

It was bought, rented, or borrowed.

With aggressive goals on the horizon, it can be tempting to acquire email lists the quick and dirty way. But sending emails to people who don’t have a prior relationship with your business will severely hurt your reputation with your prospects, your internet service provider, and your email server.

Secondly, people really don’t like being spammed. Recipients of your emails weren’t expecting to get an email from you -- and they likely didn’t want to get an email from you. Many of them will mark your message as spam, which hurts the Sender Score of the servers you send from. This taints your IP reputation and makes it harder for your future emails to get delivered. Many email service providers will cut off senders that violate certain limits because of the impact on IP reputation and delivery. You’ll also put your company in jeopardy because you’re all on the same IP address, and those can take months to recover.

Plus, you’ll be known as a spammy marketer -- and you’re better than that!

There are other options people can take besides hitting “spam” -- and they can hurt almost as much. According to the 2014 Science of Email report, The most common responses to unwanted email are, in order: 1) ignore or delete, 2) unsubscribe, and 3) mark as spam. This isn’t good news: ignoring or deleting emails are also terrible for your reputation and can cause you to get caught in spam filters more often and will reduce your conversion rates.

It has steroidal growth.

The size of your list doesn't account for the quality of email addresses on it. Steroidal growth of email lists either means your team is buying or renting email lists, or there are bots filling out your forms. List quality suffers significantly either way.

It's old.

Good email addresses are like bread: they go stale if they’re left alone for too long. It’s not you, it’s them: email marketing databases naturally degrade by about 22.5% every year as contacts switch companies, change Internet service providers, and abandon old email addresses. This is a reality every email marketer faces and it means you have to add more (quality!) contacts to your lists continually.

It has a high bounce rate.

When an email bounces, it means it was unable to be delivered to a recipient’s inbox. Bounce rates are usually high if your lists are full of purchased, invalid email addresses. This is yet another signal to Internet service providers that you’re a spammy marketer, and they can block you so your emails are never delivered.

Hard bounces are recorded when an email is considered permanently undeliverable, which can happen if it was sent to an invalid or blocked email address. Your email service provider might automatically remove these contacts from your lists, but double check to make sure. Shoot for a hard bounce rate of less than 5%.

Soft bounces, on the other hand, are recorded when an email is considered temporarily undeliverable. This can happen when someone has an auto-responder set or their inbox is full. Keep them on your list, but monitor them -- if their soft bounce rate doesn’t decrease, then the email address is probably inactive and you should remove it from your list.

Now that you know what not to have in your email lists, let’s take a look at what makes a list good.

What a Good Email List Looks Like

It is permission-based.

Your email marketing strategy isn’t inbound if it’s not permission-based. Inbound marketing is about trust, value, and relevancy. By only sending emails to people who have given us permission to do so, we build trust and foster credibility with our subscribers and prospects. (Oh, and there’s a law part, too.)

The good folks who build permission-based email lists have opt-in strategies so people subscribe to their emails by choice -- meaning somewhere along the way, they were asked or required to sign up in exchange for the promise of compelling content. (More on opt-in strategies in a second.)

It includes regular and recent emailings.

To maintain clean email lists, you need to send emails regularly and update the lists as they decay over time. This helps to maintain communication with your subscribers so they remember they opted in. Even when people chose to opt in to your list, if they haven’t heart from you for a while, they may forget they subscribed.

Alright, so you know how to spot a good and bad email list. So how does a well-intentioned marketer turn their bad email lists into good ones?

How to Make a Bad List Good

1) Segment the list by email address age.

Segmenting lists by how long someone’s been in your database lets you prioritize sending emails to contacts while they’re still fresh.

Start by digging into your most recent email list and assigning an age to each of your contacts. To do this, use either the date the contact became a subscriber, the last interaction date, the date of the contact’s source, or another age indicator.

Next, decide how refined you want your segmentation to be. The more granular, the more personalized your different campaigns will be. But don’t go overboard – you don’t want to end up with a segment of 10 contacts because the return on effort will be low.

2) Build an opt-in strategy.

Opt-in strategies allow people to subscribe to your emails by choice, which will increase the quality of your lists over time. The first step to creating a successful opt-in strategy is to create helpful, original content that your buyer personas (aka target audience) will love to read on a regular basis. Next, find ways to ask or require people to subscribe to email updates.

The “ask" method is when you give people the option of subscribing to your content via email, but it’s not required to do so to consume it. A great example would be a check mark on a landing page form asking if you want to subscribe to the company’s blog. At HubSpot, we increased our blog email subscribers by 128% by putting a check box on our landing pages.

The “require” method means gating premium content offers like ebooks, reports, and templates behind a form that requires this personal information.

3) Create a re-engagement campaign.

Do a chunk of your email subscribers never open or click through your emails? Don’t throw in the towel just yet. First, identify the email addresses who haven’t engaged with your emails in several years and remove them altogether, as they will likely increase spam complaints.

Then, try to reinvigorate the rest of your list with a re-engagement campaign. To do this, create a compelling opt-in email message that gives readers the choice of opting in to your emails – otherwise, they’ll be removed from your list after that mailing. Use this opportunity to ask for feedback, too, so you can learn how to better customize your email marketing to their interests and needs.

4) Remove all the unengaged folks.

Your re-engagement campaign won’t work on everyone. Don’t be sad – when it comes to your email subscribers, you want quality over quantity. Your open rate will improve when you send emails to people you actually want to open your emails. After some time, remove all contacts that still didn’t open your emails so you don’t affect your future deliverability rates.

A report from Experian shows that every dollar invested in email marketing initiatives yields about $44.25 return -- but to cash in on your email marketing efforts, you’ve got to maintain honest, clean lists. If you remember anything from this blog post, here are three things you need to know to determine if the list is quality:

Where you got the list

Whether you have permission to email these people

What expectations the people on your list have for how much email you'll send them

So if you want that kind of ROI for your email marketing, make sure your lists are squeaky clean before your next send.

Hi Lindsay, Grow lists organically, patiently, to see lasting results. Quality lists trump any bought list, because subscribers usually trust you before signing up. Not so with bought lists. Thanks for the tips!